Clio squirming about with inner pain (5)
I believe the answer is:
colic
'inner pain' is the definition.
(I've seen this before)
'clio squirming about' is the wordplay.
'squirming' is an anagram indicator (I've seen this in other clues).
'about' becomes 'c' (abbreviation for 'circa').
'clio' is an anagram of 'coli'.
'coli'+'c'='COLIC'
'with' is the link.
(Other definitions for colic that I've seen before include "Severe stomach pain" , "Intestinal infection" , "Intestinal pain" , "gut reaction" , "Gastric pain" .)